"It literally just happened," a source told Malkin, who did not report Gabby's hosting date.

The most likely date is the currently host-free April 24 episode, which will also welcome musical guests MGMT.

The actress' role in "Precious" may have been a serious one, but Gabby showed her comedic chops on the red carpet and on late night shows in recent months – and while radio host Howard Stern himself took aim at her earlier this month, stating that her weight would keep her from further work, it appears she will have the last laugh.

Beyond "SNL," the young actress has also lined up a recurring TV role alongside Laura Linney on Showtime's "The Big C," premiering this August. She has also completed the upcoming independent film, "Yelling to the Sky."